Phrachao Siribounyasan (Lao: ພຣະເຈົ້າສິຣິບຸນຍະສາຣ; Thai: พระเจ้าสิริบุญสาร; died November 1781), also known as Ong Boun (ອົງບຸນ), Bunsan or Xaiya Setthathirath III,[1] was the 3rd king of the Kingdom of Vientiane (r. 1767 to 1781).
[2] The Burmese King considered Lao kingdoms as his base to expand further east.
In 1778, a Siamese army under Somdej Chao Phya Mahakasatsuek (later Rama I) invaded Vientiane.
[4] Ong Boun fled into jungle, finally, he decided to submit to the Siamese.
[5] However, Ong Boun revolted against Siam in 1780, he killed the Siamese appointed governor Phraya Supho.